Agnieszka Krata

Inductively coupled plasma mass spectrometry in comparison with neutron activation and ion chromatography with UV/VIS detection for the determination of lanthanides in plant materials

Analytical performance of inductively coupled plasma mass spectrometry (ICP-MS) for determination of lanthanides in plant materials was investigated and compared with neutron activation analysis (NAA) as well as ion chromatography (IC) with UV-VIS detection. Two sample preparation protocols were tested: (i) microwave assisted digestion by concentrated nitric acid; (ii) microwave digestion involving silica and fluoride removal, followed by the selective and quantitative lanthanides group separation from the plant matrix. Several Certified Reference Materials (CRM) of plant origin were used for the evaluation of the accuracy of the applied analytical procedures. The consistency of results, obtained by various methods, enabled to establish the tentative recommended values (TRV) for several missing elements in one of CRMs. The ICP-MS, due to its very high sensitivity, has the potential to contribute to this aim. The discrepancy of the results obtained by various methods was discussed in a view of possible matrix effects related to the composition of investigated materials.

On-line separation of strontium from a matrix and determination of the 87Sr/86Sr ratio by Ion Chromatography/Multicollector-ICPMS

In this work a high throughput, robust and sensitive method for the precise isotopic analysis of 87Sr/86Sr by coupling Ion Chromatography (IC) and Multicollector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) is presented. The effective separation of Sr from a sample matrix by IC enables on-line isotopic determination of the 87Sr/86Sr ratio in transient signals by MC-ICPMS, without laborious off-line and time consuming sample preparation step and the need for clean room facilities. Mass discrimination and instrument drift were corrected by using the natural constant 86Sr/88Sr ratio as an internal standard. A precision (2σ) of the 87Sr/86Sr ratio of 0.003% was achieved in natural fresh water and high salinity samples, e.g. Dead Sea water, as well as carbonate and silicate rocks. Robustness, relatively high precision and accuracy, as well as minimum possibility of sample contamination of the developed analytical method have been demonstrated in complex natural samples of water and rocks as well. This method for the first time reports a possibility of isotopic analysis of cations by on-line IC separation with precision close to that obtained by an off-line technique.

High precision direct analysis of magnesium isotope ratio by ion chromatography/multicollector-ICPMS using wet and dry plasma conditions

In this work the applicability of Ion Chromatography (IC) coupled to Multicollector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) for on-line magnesium isotope ratio analysis was explored. Various instrumental setups were employed to enable continuous magnesium separation from the sample matrix by IC followed by MC-ICPMS. The performance of two separation columns IonPac CS16 (ID 5mm or ID 3mm) connected with appropriate CERS 500 suppressors (4mm or 2mm) using dry and wet plasma conditions was compared. With the use of ID 3mm column and 2mm suppressor it was possible to apply dry plasma mode with Aridus II desolvation system. Mass discrimination and instrument drift were corrected by sample-standard bracketing method using the 26Mg/24Mg isotope ratio of DSM-3 as standard. Good accuracy and high precision of the magnesium isotope ratio (generally 0.15‰ (2SD)) were achieved for wet and dry plasma modes; both were comparable to off-line Mg separation and continuous measurement. The sensitivity of MC-ICPMS measurements with dry plasma was 25 times higher in comparison to wet plasma conditions. Robustness and applicability of the method was demonstrated for matrix-rich natural water and rock samples magnesium isotope analysis.

On the use of certified reference materials for assuring the quality of results for the determination of mercury in environmental samples

This work focused on the development and validation of methodologies for the accurate determination of mercury in environmental samples and its further application for the preparation and certification of new reference materials (RMs). Two certified RMs ERM-CC580 (inorganic matrix) and ERM-CE464 (organic matrix) were used for the evaluation of digestion conditions assuring the quantitative recovery of mercury. These conditions were then used for the digestion of new candidates for the environmental RMs: bottom sediment (M_2 BotSed), herring tissue (M_3 HerTis), cormorant tissue (M_4 CormTis), and codfish muscle (M_5 CodTis). Cold vapor atomic absorption spectrometry (CV AAS) and inductively coupled plasma mass spectrometry (ICP MS) were used for the measurement of mercury concentration in all RMs. In order to validate and assure the accuracy of results, isotope dilution mass spectrometry (IDMS) was applied as a primary method of measurement, assuring the traceability of obtained values to the SI units: the mole, the kilogram, and the second. Results obtained by IDMS using n(200Hg)/n(202Hg) ratio, with estimated combined uncertainty, were as follows: (916xa0±xa041)/[4.5xa0%] ngxa0g−1 (M_2 BotSed), (236xa0±xa014)/[5.9xa0%] ngxa0g−1 (M_3 HerTis), (2252xa0±xa054)/[2.4xa0%] ngxa0g−1 (M_4 CormTis), and (303xa0±xa015)/[4.9xa0%] ngxa0g−1 (M_CodTis), respectively. Different types of detection techniques and quantification (external calibration, standard addition, isotope dilution) were applied in order to improve the quality of the analytical results. The good agreement (within less than 2.5xa0%) between obtained results and those derived from the Inter-laboratory Comparison, executed by the Institute of Nuclear Chemistry and Technology (Warsaw, Poland) on the same sample matrices, further validated the analytical procedures developed in this study, as well as the concentration of mercury in all four new RMs. Although the developed protocol enabling the metrological certification of the reference value was exemplified by the determination of mercury in environmental samples, it could be considered as valid for any certification procedure required whenever new certified RMs are introduced.

Direct determination of δ44/42Ca isotope ratio by ion chromatography/low-resolution multicollector ICPMS

High-precision on-line procedure for measurement of calcium isotopic ratio by coupling ion chromatography to multicollector inductively coupled plasma mass spectrometry was developed. Calcium separation from the sample matrix was achieved on an ion chromatography column-IonPac CS16-ID 3xa0mm connected with CERS 500 2xa0mm suppressor and followed by multicollector inductively coupled plasma mass spectrometry calcium isotopic ratio determination. Dry plasma mode was used with Aridus II desolvation system. To sustained samples with high level of total dissolved salts as well as account capacity of applied analytical column, the method has been optimized regarding calcium isotope ratio measurements with low-resolution mass spectrometry. Mass discrimination and instrument drift were corrected by sample-standard bracketing method using the 44 Ca/42 Ca isotope ratio of SRM 915a as a standard. Good accuracy and reasonable precision of calcium isotope ratio (generally 0.20‰ [2SD]) were achieved, which are comparable to off-line Ca separation and continuous measurement. The reproducibility of the proposed analytical procedure was verified by measuring the SRM 915a standard as a sample randomly over 3xa0months (nxa0=xa056). Applicability of the protocol was demonstrated for matrix-rich natural water samples, coral samples, and bone standard reference materials.